The goal of this SBIR is to provide proof-of-concept of Vetigenics? canine-derived scFv phage display platform for rapid, cost effective production of highly versatile, canine-derived scFvs. scFvs against CD19, CD3 and CTLA4, three high-value, immunological molecules being targeted by antibody-based strategies in human cancer immunotherapy, will be isolated. Selected scFvs will be sequenced and binding affinities determined. Through its collaborators at the University of Pennsylvania School of Veterinary Medicine, Vetigenics has access to canine cells, cell lines and tissues providing an unparalleled ability to validate isolated scFv. Target specificity and functionality of isolated scFvs will be validated using standard immunological assays. To demonstrate the versatility and broad applicability of the scFv format, a lead canine CD19-specific scFv will be selected and used to generate 1) canine CAR T cells and 2) monoclonal antibodies. CD19-specific scFv formats will be validated for specificity, functionality and in vitro diagnostics including flow cytometry and immunohistochemistry. Successful completion of this work will provide validated reagents for in vivo use in dogs with cancer, enabling exploration of combination approaches and correlative biomarkers of response in a clinically relevant large animal cancer model. In addition, this work will provide parallel promising immunotherapeutics for the veterinary market.